Stuck on ASQ CQE Questions

Hello! My husband is going to take the ASQ CQE in a few weeks. There are a few questions from the two official ASQ CQE exams that he does not understand. Can someone help us figure out the logic behind these tests? Also, I recently discovered five sample CQE tests online from a place called IE&MS Research Center, which as far as I can tell, is a Korean company. Here’s the first one: http://www.iems.co.kr/CQE/cqedb/cqeproblem/CQEproblem1.pdf (There are five total, just change the “1” in the URL.) I’ve noticed with ASQ exams, a lot of the study guides don’t correlate to the actual test at all. Curious if anyone is familiar with these exams and if they are valuable to the actual test?

1. In a complex electronic system containing 1,000 devices in series, an increase in component reliability from 99.90% to 99.99% would improve the system reliability by a factor of approximately… the correct answer is 2.5, but we don’t know how that was solved.

2. A data set for a measured characteristic of a part has a standard deviation of 11.2. If the standard deviation of the measurement error is 2.1, what is the estimated true standard deviation for the characteristic? The correct answer is 11.0, but again, not sure how to solve it.

3. A process with a binomial distribution has a 5% probability of success. If 10 samples are drawn from the process, what is the approximate probability of having zero success? The correct answer is 0.6.

4. An internet service provider logged four primary types of complaints over a one-month period. A team used the data to create the following incomplete table. What test statistic should be used in a goodness-of-fit analysis?